The present invention relates to electronics, more particularly to semiconductor devices and related methods, and most particularly to III-N type devices in which both enhancement- and depletion-mode devices are made available by patterned dopant ions.
Many field effect transistors (FETs) operate in an ON state at zero applied gate voltage; such transistors are called “depletion-mode.” “Enhancement-mode” FETs are those which are in an OFF state at zero applied gate voltage.
An important area of research in semiconductor devices has been the search for a semiconductor technology using a material with a wider bandgap than silicon. Wider bandgap materials have the potential to operate at higher temperatures and higher breakdown voltages. Many years of research and development have been invested in III-V compound semiconductors, such as GaAs and related compounds (InP, AlGaAs, etc.).
In recent years the family of “III-N” semiconductors has been an area of intense development. GaN provided the first blue LED, and such LEDs are now in commercial use. Development of transistors or other active devices in this materials system is very attractive, because of the high bandgaps available (e.g. 3.4V for GaN, and higher for AlGaN alloys).
A difficulty in achieving III-N active devices was the lack of enhancement-mode devices. A key breakthrough in this area was achieved by the present inventor and colleagues, using fluorine implantation to introduce fixed charge into the top (higher-bandgap) layer of a HEMT-like device. These techniques are described in published U.S. patent applications 2007-0295993, 2007-0228416, and 2007-0278518, all of which are hereby incorporated by reference in their respective entireties for all purposes.
Note that the points discussed above may reflect the hindsight gained from the disclosed inventions, and are not necessarily admitted to be prior art.